Last fall one of my upstairs toilets started making a noise similar to releasing pressure when the master bath shower is on, the dishwasher or washing machine downstairs is on. It only happens when water is running in another part of the house. The home is 6 years old. This does not happen in the master bath or the powder room downstairs. Sometimes the noise is very loud and can be heard throughout the house. our builder told us this may happen occasionally, but it now happens on a daily basis.